Specifying Use Case Interaction: Types of Alternative Courses

Use cases are a powerful and widely recognised tool for the elicitation and specification of functional software requirements. However, major problems and gaps still exist; practitioners frequently encounter these. One of these is the specification of alternative use case interaction courses. Experience shows that practitioners do not only need to specify alternative interaction courses that are inserted subject to a business condition; they also need to express partially or fully parallel interaction courses, exceptional use case behaviour, and cyclic interaction paths. Based on an extensive literature review and practical observations, this paper provides definitions for types of alternative interaction courses, as well as clarifying conceptual differences between, and providing illustrative real-world examples of, each. Moreover, these definitions are related to Cockburn’s relevant practical approach of use case goals and use case business results in the context of goal-driven requirements engineering. Finally, the provided definitions will contribute to an understanding of use case interaction specification and goal-driven requirements engineering in practice; they also present clear advice on how to perform use case model refactoring through the application of UML’s repeatedly discussed extend-relationship.